Water-dispersible composite structure

Abstract

Water-dispersible composite structure comprising a fiber layer, characterized by the fact that - at least part of the fiber layer consists of a fiber fabric or sheet containing 50-90 wt.% wood fibers, 10 to 50 wt.% non-wood fibers and 0.1-20 wt.% binder, calculated by weight of the fibers, wherein at least part of the binder is a water-soluble polymer, and - where the fiber fabric or sheet is produced using wet forming technology, wherein a first part of the binder is formed by a water-soluble polymer or a polymer mixture and a second part of the binder is formed by a water-dispersible polymer or a polymer mixture, and wherein the binder contains at least one water-soluble polymer and at least one water-dispersible polymer in a weight ratio of 1:20-20:1, calculated on the basis of the dry mass of the polymers.

Description

Field of the invention

[0001] The present invention relates to fibrous structures, such as sheet-like or web-like layered materials made from fibrous raw materials. Such materials can be separately dispersed in an aqueous medium to obtain at least a portion of the fibers of the raw material that can be recovered. More specifically, the present invention relates to structures made of fibers of natural and synthetic origin that form composite materials that can be dispersed in aqueous media. State of the art

[0002] Dispersible nonwovens are well-known in the field. They are used as dispersible and flushable materials for hygienic applications.

[0003] US 5,346,541 teaches water-dispersible formulations and materials, as well as methods for influencing their water dispersibility. The water-dispersible formulations comprise from 1 to 90% by weight of at least one water-soluble cellulose ether binder. In addition, the formulations contain at least about 10 to about 99% by weight of long cellulose fibers having a length of greater than about 300 micrometers to about 2 millimeters or more. The document states that the inclusion of significant amounts of long cellulose fibers increases the water dispersibility of water-soluble cellulose ether binders. Release agents that release gases can be added to increase the water dispersibility of the formulations.

[0004] The use of the materials in the healthcare and food industries is recommended.

[0005] US 3,563,241 discloses absorbent, textile-like structures for single-use use that exhibit strength and durability that allow for proper use, yet can still be disposed of in wastewater systems after use. The structure consists of water-sensitive fibers with ionizable groups; the materials can be selected, for example, from cyanoethylcellulose or hydroxyethylcellulose.

[0006] Other flushable wipes are described in US Patent Nos. 5,629,081 and EP 1 285 985.

[0007] US 2014 / 0318726 discloses a web comprising wood pulp and solvent-spun fibers that can be used in rapidly dispersible wet wipes. The solvent-spun fibers comprise fibrillated cellulose fibers, for example, of the Tencel type. In the examples of the patent application, a mixture of groundwood and Tencel short-cut fibers was used to produce wet-laid fabrics. The fibers are refined, 1% CMC is added as a dispersing aid, and an epichlorohydrin-based wet-strength resin is added to increase wet strength. The resulting slurry is then wet-laid, e.g., on a paper machine, to form a sheet. The sheet then undergoes a hydroentangling process, either online or as a separate offline process, to form a web.

[0008] The resulting wipes are designed to be flushable through a standard toilet system and to decompose into biodegradable, dispersible fragments after disposal.

[0009] Although the disclosed materials are dispersible in water, they are designed for use as disintegrating and disposable materials (single-use materials). For this reason, the known dispersible materials still lack strength and structural integrity compared to corresponding non-disintegrating materials. Therefore, their primary application is in products that already allow complete decomposition in wastewater and sewage systems. The materials they contain are therefore wasted after use and cannot be recycled.

[0010] The use of hydroentanglement in this field compromises the reprocessing of the material for recovery and recycling of the individual materials.

[0011] There is a need for dispersible structural materials that exhibit good mechanical properties and yet can be dispersed in aqueous phase by conventional recycling processes used in the paper and board industry to obtain fractions of the fiber constituents and be recycled. Brief description of the invention

[0012] The aim of the present invention is to provide novel water-dispersible compositions and structures comprising at least one layer, for example a plurality of overlapping layers consisting of fiber webs or films.

[0013] The present invention is based on the concept of producing by wet forming a fibrous layer containing wood fibers, natural and / or synthetic non-wood fibers, and a binder. Surprisingly, it has been discovered that a water-dispersible film or sheet with mechanical properties can be produced by providing a fibrous composition comprising at least 50% wood fibers in a mixture with natural and / or synthetic fibers, and by bonding the fibers together using a binder compatible with wet forming and comprising a water-soluble polymer and a water-dispersible polymer.

[0014] The present materials can be produced by wet forming in the following steps: - conveying an aqueous fibre slurry to a carrier; - Draining liquid through the carrier to form a fiber layer; and - applying a binder to the fiber layer to at least partially bond the fibers together, wherein the binder comprises an aqueous solution of a water-soluble polymer and also contains a water-dispersible polymer.

[0015] The compositions and process can be used to produce nonwoven products such as nonwoven webs and nonwoven films.

[0016] More specifically, the present invention is mainly characterized by what is disclosed in the characterizing parts of the independent claims.

[0017] Significant advantages are achieved by the present invention. Thus, the present materials exhibit good mechanical properties, which enable their use in typical paper, board, and nonwoven applications. In particular, the present invention can be used to produce nonwoven products selected from the group of webs and sheets.

[0018] Furthermore, the materials can be dispersed in a conventional pulper, such as those used in the paper or board industry, to separate at least the wood fibers from the water-dispersible material. Due to the structure of the materials, the wood fibers can be at least partially recovered and, if desired, recycled for use in fiber materials and other materials.

[0019] Wet forming can be carried out industrially, for example on a nonwovens or paper machine.

[0020] The bonding takes place without mechanical connection such as hydroentanglement or spun-lacing.

[0021] The embodiments of the present technology will be discussed in more detail with reference to the accompanying figures. Brief description of the drawings Fig. 1 is a micrograph showing, on the left, the assumption of a reference material and, on the right, the individual fiber of such a material; and Fig. Figure 2 is a micrograph showing, on the left, the assumption of a material according to the present technology and, on the right, the individual fiber of such a material. Embodiments

[0022] As discussed above, the present technology provides composite structures in the form of water-dispersible fiber layers containing natural fibers, such as wood fibers in combination with natural or synthetic fibers.

[0023] In one embodiment, the nonwoven fabric or fibrous web in the water-dispersible composite structure comprises a network of fibers held together primarily by hydrogen bonds and adhesive bonds.

[0024] In this context, the layers are referred to as “composite structures” because they contain both natural and synthetic fibers.

[0025] "Water-dispersible" in connection with the materials in question means that the fiber matrices can be broken up and the fiber materials can be separated from the materials and from each other. Thus, at least a portion, e.g., at least 5%, in particular at least 10%, at least 20% by weight, of the wood fibers or other natural fibers can be recovered and, where appropriate, recycled.

[0026] In one aspect, water dispersibility refers to the properties of the material that enable it to be industrially recycled under the conditions used in the recycling of paper, board, and other fiber-based products. For example, typical conditions for pulping low-consistency (LC) pulps are a consistency of 2 to 7 wt.% and a temperature of 30 to 60°C. Typical conditions for pulping high-consistency (HC) pulps are a consistency of 10 to 35 wt.% and a temperature of 30 to 60°C. The pulping time depends on the design of the industrial pulper, such as the dimensions of the equipment and the rotor used for pulping. Typically, the pulping process is continued until an appropriate amount of fiber is extracted from the original material structure.The pulping process may include chemicals such as NaOH, H2O2, chelating agents, sodium silicate and surfactants.

[0027] According to one embodiment, the water-dispersible composite structure comprises natural fibers in the form of "wood fibers." In one embodiment, such wood fibers are selected from bleached and unbleached, refined and unrefined, particularly unrefined, fibers selected from the group of chemical pulp fibers, recycled fibers, mechanical pulp fibers, and semi-mechanical pulp fibers, and combinations thereof.

[0028] The wood material can be birch, beech, aspen (e.g., European aspen), alder, eucalyptus, maple, acacia, mixed tropical hardwood, pine (e.g., incense pine), fir, hemlock, larch, spruce (e.g., black spruce or Norway spruce), or a mixture thereof.

[0029] The second fiber component(s) of the present composite structures are non-wood fibers. Such fibers can be natural fibers, e.g., annual plant fibers, or synthetic fibers, or combinations thereof. Synthetic fibers can also be referred to as "man-made," in contrast to wood fibers and natural non-wood fibers, which are considered non-synthetic fibers in this context.

[0030] In one embodiment, the non-wood fibers are selected from the group consisting of fibers obtained from plant materials other than wood (also referred to as natural non-wood (or “non-woody”) materials) and from artificial fibers, such as synthetic fibers, in particular polymer fibers.

[0031] The non-wood fibers can be selected from the following groups, for example: - annual or perennial plant fibres, such as hemp, flax, kenaf, bagasse, cotton, straw; - thermoplastic fibers, for example polylactides (PLA), glycolic acid polymers (PGA), polyhydroxyalkanoates (PHA), polyolefins (PO), polyethylene terephthalates (PET), polyester fibers (PES), polyvinyl alcohol fibers (PVA); - bicomponent fibres comprising thermoplastic polymers; - mineral fibers, glass fibers; - regenerated cellulose fibers, such as viscose fibers, lyocell fibers, and rayon fibers; and combinations of fibers selected from two or more of the aforementioned groups.

[0032] In one embodiment, the non-wood fibers, in particular the synthetic fibers, are "short-cut fibers." In the present context, "short-cut fibers" are fibers with a length of 5 to 25 mm, in particular 6 to 18 mm. In one embodiment, they can have a thickness of 0.5 dtex to 20 dtex, in particular 1 to 15 dtex, for example 1.5 to 10 dtex.

[0033] The fibres of annual or perennial plants may be in the form of short-cut fibres (as defined above) or fibres obtained by defibration, including mechanical, semi-mechanical or chemical defibration, of the corresponding plant materials.

[0034] In one embodiment, the fiber layer is formed by a nonwoven fabric or fiber web containing 50-90 parts by weight of wood fibers together with 0 to 90, for example, 10 to 90 parts by weight of annual or perennial plant fibers and 0 to 50, for example, 10 to 50 parts by weight of synthetic short-cut fibers or combinations thereof. The total amount of non-wood natural fibers and synthetic fibers is typically 10 to 50 parts by weight.

[0035] In one embodiment, 50 to 99 wt.%, in particular 60 to 90 wt.%, of the fibers of the fiber layer consist of cellulose or lignocellulose fibers or mixtures thereof and 1-50 wt.%, in particular 10-40 wt.%, of chemical fibers.

[0036] In one embodiment, 50 to 99 wt.%, in particular 60 to 90 wt.%, of the fibers of the fiber layer consist of cellulose or lignocellulose fibers or mixtures thereof and 1-50 wt.%, in particular 10-40 wt.%, of non-wood natural fibers, such as fibers from annual or perennial plants, or of such fibers in combination with artificial fibers.

[0037] In one embodiment, the artificial fibers are selected from the group of regenerated cellulose fibers, synthetic fibers, synthetic thermoplastic fibers and mixtures thereof.

[0038] The regenerated cellulose fibers can be selected from the group of viscose fibers, lyocell fibers, rayon fibers, and mixtures thereof. The thermoplastic fibers are selected from the group of polyolefin fibers, polyester fibers, and biopolymer fibers, and mixtures thereof.

[0039] In one embodiment, annual and other non-woody natural (typically plant) fibers are selected from the group consisting of cereal straws, wheat straw, reed canary grass, reeds, flax, hemp, kenaf, jute, ramie, seeds, sisal, abaca, coconut, bamboo, bagasse, cotton kapok, milkweed, pineapple, cotton, rice, reeds, esparto grass, Phalaris arundinacea, and combinations thereof. Other non-woody fibers are selected from the group consisting of seed hair fibers, leaf fibers, and bast fibers.

[0040] In one embodiment, the present composite structures further comprise about 0.1 to 20 wt.%, calculated based on the dry mass of the binder and the dry mass of the fibrous portion of the fiber layer.

[0041] In this context, the term "binder" refers to a substance capable of binding fibers together in such a way that it contributes to the formation of a fiber network. The term "binder" refers to both individual substances and mixtures of substances.

[0042] In one embodiment, the present invention comprises a combination of a water-soluble polymer and a water-dispersible polymer. The water-soluble polymer is typically a hydrophilic polymer, while the water-dispersible polymer is typically a hydrophobic polymer.

[0043] In one embodiment, the binder is selected from the group consisting of polyvinyl alcohols, polyvinyl acetate dispersions, ethyl vinyl alcohol dispersions, polyurethane dispersions, acrylic latexes, styrene-butadiene dispersions, binders based on finely divided cellulose, binders based on cellulose derivatives, biopolymers such as biopolymers based on starch derivatives, natural gum latexes, alginates, guar gum, hemicellulose derivatives, chitin, chitosan, pectin, agar, xanthan, amylose, amylopectin, alternan, gellan, mutan, dextran, pullulan, fructan, locust bean gum, carrageenan, glycogen, glycosaminoglycans, murein, bacterial capsular polysaccharides and the like, and combinations thereof.

[0044] The present invention comprises the use of a binder comprising a combination of - a first part of the binder consisting of a water-soluble polymer or a mixture of such polymers; and - a second part of the binder consisting of a water-dispersible polymer or a polymer mixture.

[0045] In one embodiment, the weight ratio between the first part (formed by the water-soluble polymer or the mixture of such polymers) and the second part (formed by a water-dispersible polymer or a polymer mixture) is 1:20-20:1, in particular 1:10 to 10:10, for example 1.5:10 to 2:20.

[0046] The binder, which comprises both a water-soluble polymer and a water-dispersible polymer, forms at least a part, preferably a major part, in particular 75 to 100 wt.%, advantageously 90 to 100 wt.% of the total binder used to form the fiber layer of the water-dispersible film or web.

[0047] As mentioned above, the water-dispersible composite structure comprises a network of fibers held together primarily by hydrogen bonds and adhesive bonds. However, other components may also be present that modify the properties, particularly the chemical or physical properties, or both, of the fiber network.

[0048] In one embodiment, the fibrous web or sheet further contains a sizing agent, particularly a reactive sizing agent. Examples of such agents are alkyl ketene dimer (commonly abbreviated to "AKD") and alkenyl succinic anhydride ("ASA").

[0049] The sizing agent can be added separately. However, in one embodiment, the sizing agent is mixed with the binder(s).

[0050] The sizing agent may be added in amounts of 0.01 to 10%, in particular 0.1 to 5%, for example 0.15 to 3%, based on the dry weight of the fibre layer.

[0051] In one example, a method for producing a water-dispersible composite structure containing a layer of wood fibers, short-cut fibers, and a binder or binder composition comprises the following steps: - conveying an aqueous fibre slurry to a perforated support, e.g. a conventional wire for wet forming; and - draining liquid through the perforated support to form a fiber layer; and - Applying a binder to the fiber layer to at least partially bond the fibers together.

[0052] Typically, the fibers in the existing fiber layers form a fiber network through hydrogen bonds and / or adhesive bonds.

[0053] In one example, the fiber layer is dried at an optional time and optionally calendered to form fiber webs or sheets.

[0054] In one example, the above process is carried out on a paper or board machine or on a wet-laid nonwoven machine.

[0055] Typically, the process is free of any hydroentanglement steps.

[0056] In one example, the binder is applied to the fiber layer as a foamed aqueous composition. Such a composition may comprise an aqueous solution of a water-soluble polymer further containing a dispersed water-dispersible polymer.

[0057] In one example, the fiber slurry applied to the screen or other porous support comprises artificial fibers or natural non-wood fibers, or combinations thereof, along with cellulose fibers, lignocellulose fibers, or a mixture thereof. The consistency of the aqueous slurry is, for example, 0.01 to 5 wt.%, in particular 0.1 to 2 wt.%.

[0058] In one example, a binder composition is added in an amount of 0.1 to 20 wt.%, for example 0.1-15 wt.%, in particular 1.5 to 10 wt.% of a binder, calculated on the basis of the dry mass of the binder and the dry mass of the fibrous part of the fiber layer.

[0059] In one example, the binder is applied to the fiber layer "at a predetermined stage." Thus, the binder can be applied to the fiber layer before it is dried to final drying or only afterward.

[0060] In one example, the binder is applied to the fiber layer with a moisture content of 90 to 10%.

[0061] In one example, the binder is applied to the fiber layer at a moisture content of about 85 to 65 wt.%. In another embodiment, the binder is applied to the fiber layer at a moisture content of about 2 to 10 wt.%.

[0062] In one example, the binder is applied to the fiber layer prior to its pressing. Such pressing is preferably performed to effect water removal and prior to further drying and calendering.

[0063] Regardless of the application time, in one example, the binder is applied to the fibrous layer, which typically has a moisture content of less than about 10 wt.%, with a doctor blade or an applicator roller. In another embodiment, the binder is applied to the fibrous layer, which typically has a moisture content of 60 wt.% or more, by a vacuum-enhanced process, by a non-contact application, or by combinations thereof.

[0064] The binder is applied to at least one side, preferably to both opposite sides of the fiber layer or alternatively or additionally using suction or negative pressure (“vacuum”).

[0065] As mentioned above, the "binder" may comprise one or more substances. It may be applied as an aqueous solution or as an aqueous dispersion, or as a mixture thereof.

[0066] In one embodiment, the binder comprises an aqueous composition having a dry matter content of 1 to 50%, for example 1 to 30%, in particular 2.5 to 25% by weight, and containing at least one water-soluble polymer and at least one water-dispersible polymer.

[0067] The binder contains at least one water-soluble polymer and at least one water-dispersible polymer in a weight ratio of 1:20-20:1, in particular 1:10-10:10. The weight ratio is calculated based on the dry weight of the polymers.

[0068] Of the binders listed above, polymers selected from the group of polyvinyl alcohols, polyvinyl acetate dispersions, ethyl vinyl alcohol dispersions, polyurethane dispersions, acrylic latexes, styrene-butadiene dispersions, binders based on finely divided cellulose, binders based on cellulose derivatives, biopolymers and combinations and mixtures thereof are particularly advantageous.

[0069] In one embodiment, the binder is thus an aqueous composition obtained by dissolving a water-soluble polymer in water to form an aqueous solution of the polymer and then dispersing a water-dispersible polymer in the aqueous solution.

[0070] The binder may, for example, comprise an aqueous composition prepared by the following steps: firstly, at least one water-soluble polymer selected from the group consisting of polyvinyl alcohol and polyvinyl acetate and combinations thereof is dissolved in water at a temperature of 10 to 100°C, in particular 15 to 100°C, at ambient pressure to form an aqueous solution of the polymer, and then at least one polymer selected from the group consisting of polyurethane dispersions, acrylic latexes, styrene-butadiene dispersions is dispersed into the solution at a temperature of 20 to 100°C at ambient pressure.

[0071] The binder composition can be prepared in a mixer or disperser by intensively mixing the aqueous phase and, if necessary, subjecting it to shear forces.

[0072] Preferably, the binder is provided as a stable dispersion.

[0073] In one embodiment, "stable dispersion" means that less than 20%, in particular less than 10%, suitably less than 5%, of the weight of the dispersed solid settles out of the dispersion when left to stand at room temperature for 24 hours.

[0074] In one embodiment, the dispersion further contains a dispersant. Such an agent may be present in an amount of up to 5%, in particular up to 2.5% by weight of the solids of the dispersion.

[0075] In one example, the binder composition obtained by dispersing a water-dispersible polymer in an aqueous solution of a water-soluble polymer is then foamed before being applied to the fiber layer.

[0076] Depending on the binders actually used, a surfactant or foaming agent may be added to achieve foaming of the composition. The surfactant or foaming agent may be added in an amount of 0.01 to 15%, particularly 0.1 to 10% by weight of the dispersion. In one embodiment, however, the aqueous composition is foamed in the absence of a surfactant.

[0077] In one embodiment, the foamed binder composition comprises 40 to 80 vol.%, in particular 55 to 75 vol.% of gas, in particular air.

[0078] The present water-dispersible composite structures typically comprise nonwovens or films with a basis weight of 10-250 g / m 2 , especially about 20-200 g / m 2 . Such nonwovens or webs are preferably selected from the group of nonwoven or paper webs and webs.

[0079] A material made using this technology exhibits excellent properties. For example, the fiber web or sheet exhibits good mechanical properties after production, achieved partly through hydrogen bonding and partly through adhesive bonding between the fibers. No hydroentanglement or hydroentanglement is required.

[0080] As mentioned above, compositions of the present type can preferably be comminuted in a pulper as is commonly used in the paper and board industry.

[0081] Thus, in one example, the nonwoven fabric or fibrous web may be dispersed in an aqueous medium upon slurrying. In one embodiment, the fibrous sheet or web may disperse in an aqueous medium, such as water, at a temperature of 10 to 75°C and a pH of 6 to 8, typically at a consistency of 1 to 40 wt.%, for example, 2 to 35 wt.%.

[0082] As the examples discussed below will show, the fibers are released due to the easy dissolution of the binder in the material during pulping and can be recovered and recycled.

[0083] The following non-limiting examples illustrate embodiments of the present technology. Example 1

[0084] In the example, one embodiment of the post-consumer simulation of a fiber matrix bonded to a binder system of water-soluble polymer, water-dispersible polymer, and hydrophobic agent according to the present technology was evaluated in a pilot environment.

[0085] For the test, 450 kg of fiber matrix bonded to a binder system was produced in a pilot wet molding process. The fiber matrix according to the present invention contained the following components: Fiber components: - Bleached softwood kraft pulp, unrefined: 60% by weight of the fiber matrix - Chemical fibers with a length of 6 mm and a thickness of 1.7 dtex: 30% by weight of the fiber matrix Binder system: - Water-dispersible polymer: 12 wt.% of the binder system - Water-soluble: 4% by weight of the binder system - Hydrophobic agent: 1.00 wt.% of the binder system

[0086] After production, the resulting material was repulped in an OptiSlush bale pulper equipped with a JP rotor and a 20 mm diameter screen plate. The pulping conditions were as follows: - Consistency: 7.45% - Temperature: 45 °C - Time: 20 min - pH: 6.9 - Specific energy consumption: 59.4 kWh / ton.

[0087] The amount of Somerville flakes (TAPPI T 275) was 35.3%, comparable to the amount of artificial fibers and water-dispersible polymer. The test showed that the binder system dissolves in conventional recycling systems and separates the pulp fibers. The pulp fibers can then be separated from other components in a coarse screening process and reused in new consumer products, i.e., paper. Example 2

[0088] In this example, an embodiment of the post-consumer simulation of a fiber matrix with the same components and component proportions as in Example 1 was compared with a pure softwood fiber suspension shredded from dried, unrefined softwood pulp.

[0089] The produced fiber matrix and the dried reference softwood fiberboard were disintegrated in a British pulp disintegrator manufactured by Lorentzen & Wettre according to the PTS method PTS-RH 021 / 97 (40 °C, 10 min, 3000 revolutions).

[0090] The suspension of shredded fibers and the reference suspension of softwood fibers were subjected to light microscopic examinations (Axioplan Carl Zeiss EL insert). The microscopic images show that the binder system of the unsifted, shredded fiber matrix suspension ( Fig. 1) has already been partially dissolved and the quality of the softwood pulp fibres corresponds to that of softwood fibres ( Fig. 2). Reference listPatent literature US 5,346,541 US 3,563,241 US 5,629,081 EP 1 285 985 US 2014 / 0318726 Concepts 1. A water-dispersible composite structure comprising a fiber layer, characterized in that - at least part of the fibre layer consists of a fibre fabric or sheet containing 50-90% by weight of wood fibres, 10 to 50% by weight of non-wood fibres and 0.1-20% by weight of binder, calculated on the weight of the fibres, wherein at least part of the binder is a water-soluble polymer, and - wherein the fiber sheet or fabric is produced by wet forming technology. 2. The water-dispersible composite structure according to concept 1, wherein the wood fibers are bleached or unbleached, refined or unrefined fibers selected from the group consisting of chemical pulp fibers, recycled fibers, mechanical pulp fibers, and semi-mechanical pulp fibers, and combinations thereof. 3. Water-dispersible composite structure according to concept 1 or 2, wherein the non-wood fibers are selected from the group consisting of natural non-wood fibers and artificial fibers, in particular polymer fibers, which are selected, for example, from the groups - annual or perennial plant fibres such as hemp, flax, kenaf, bagasse, cotton and straw and combinations thereof; - thermoplastic fibers, e.g. polylactides (PLA), glycolic acid polymers (PGA), polyhydroxyalkanoates (PHA), polyolefins (PO), polyethylene terephthalates (PET), polyesters (PES), polyvinyl alcohols (PVA); - bicomponent fibres comprising thermoplastic polymers; - mineral fibers, glass fibers; - regenerated cellulose fibres, such as viscose fibres, lyocell fibres, rayon fibres; and - Combinations of fibers selected from two or more of the aforementioned groups. 4. Water-dispersible composite structure according to any one of concepts 1 to 3, wherein the non-wood fibers are short-cut fibers, in particular with a length of 5 to 25 mm, in particular 6 to 18 mm, and preferably a thickness of 0.5 dtex to 20 dtex, in particular 1 to 15 dtex, for example 1.5 to 10 dtex. 5. Water-dispersible composite structure according to any one of the preceding concepts, wherein the binder is selected from the group consisting of polyvinyl alcohols, polyvinyl acetate dispersions, ethyl vinyl alcohol dispersions, polyurethane dispersions, acrylate latices, styrene-butadiene dispersions, binders based on finely divided cellulose, binders based on cellulose derivatives, biopolymers, such as biopolymers based on starch derivatives natural gum latexes, alginates, guar gum, hemicellulose derivatives, chitin, chitosan, pectin, agar, xanthan, amylose, amylopectin, alternan, gellan, mutan, dextran, Pullulan, fructan, locust bean gum, carrageenan, glycogen, glycosaminoglycans, murein, bacterial capsular polysaccharides and the like, and combinations thereof. 6. A water-dispersible composite structure according to any one of the preceding concepts, wherein a first part of the binder is formed by a water-soluble polymer or a polymer mixture and a second part of the binder is formed by a water-dispersible polymer or a polymer mixture. 7. A water-dispersible composite structure according to any one of the preceding concepts, wherein the nonwoven fabric or fibrous web comprises a network of fibers held together primarily by hydrogen bonds or adhesive bonds. 8. A water-dispersible composite structure according to any one of the preceding concepts, wherein the nonwoven fabric or sheet further contains a sizing agent, in particular a reactive sizing agent such as alkyl ketene dimer or alkenyl succinic anhydride. 9. A water-dispersible composite structure according to concept 8, wherein the sizing agent is mixed with the binder(s). 10. A water-dispersible composite structure according to any one of the preceding concepts, wherein the fiber web or sheet is capable of dispersing when slurried in an aqueous medium. 11. A water-dispersible composite structure according to any one of the preceding concepts, wherein the fiber web or sheet is dispersible in an aqueous medium at a temperature of 10 to 75°C and a pH of 6 to 8. 12. A water-dispersible composite structure according to any one of the preceding concepts, comprising a fiber fabric or sheet having a basis weight of 10-250 g / m 2 , especially about 20-200 g / m 2 . 13. A water-dispersible composite structure according to any one of the preceding concepts, comprising a fibrous web or sheet selected from the group of nonwoven webs and sheets. 14. A process for producing a water-dispersible composite structure containing a layer of wood fibers, non-wood fibers and a binder, the process comprising the steps of: - conveying an aqueous fibre slurry to a perforated support; - draining liquid through the perforated support to form a fiber layer; and - applying a binder to the fiber layer to at least partially bind the fibers, characterized in that - the binder comprises an aqueous solution of a water-soluble polymer which also contains a water-dispersible polymer. 15. The method of concept 14, wherein the binder is applied to the fiber layer as a foamed aqueous composition comprising an aqueous solution of a water-soluble polymer further containing a dispersed water-dispersible polymer. 16. A process according to concept 14 or 15, wherein the fiber pulp comprises chemical fibers and optionally natural non-wood fibers together with cellulose fibers, lignocellulose fibers or a mixture thereof, wherein the aqueous pulp has a consistency of 0.01 to 6 wt%, in particular 0.5 to 3 wt%. 17. The method according to any one of concepts 14 to 16, wherein the wet forming is carried out on a paper or board machine or on a wet nonwoven machine. 18. The method of any one of concepts 14 to 17, wherein the binder is applied to the fiber layer before the fiber layer is dried to final dryness. 19. Method according to one of concepts 14 to 18, wherein the binder is applied to the fiber layer with a moisture content of 99 to 10%, in particular 80 to 20%, for example 70 to 25% by weight. 20. The method of any one of concepts 14 to 19, comprising drying and calendering the fiber layer to form a fiber web or fiber sheet. 21. The method according to any one of concepts 14 to 20, wherein the binder is applied to the fiber layer with a doctor blade, with an application roller, by a vacuum-enhanced process or by contactless application to at least one side of the fiber layer. 22. The method according to any one of concepts 14 to 21, wherein the binder is obtained by dispersing a water-dispersible polymer in an aqueous solution of a water-soluble polymer and optionally foaming the composition thus obtained. 23. The method according to any one of concepts 14 to 22, wherein the binder comprises an aqueous composition having a dry matter content of 1 to 50%, for example 1 to 30%, in particular 2.5 to 25% by weight, and which contains at least one water-soluble polymer and at least one water-dispersible polymer. 24. The method according to any one of concepts 14 to 23, wherein the binder contains at least one water-soluble polymer and at least one water-dispersible polymer in a weight ratio of 1:20-20:1, in particular 1:10-10:10, calculated on the basis of the dry mass of the polymers. 25. The method according to any one of concepts 14 to 24, wherein the binder comprises a polymer selected from the group consisting of polyvinyl alcohols, polyvinyl acetate dispersions, ethyl vinyl alcohol dispersions, polyurethane dispersions, acrylic latexes, styrene-butadiene dispersions, binders based on finely divided cellulose, binders based on cellulose derivatives, biopolymers, and combinations thereof. 26. The method according to any one of concepts 14 to 25, wherein the binder is an aqueous composition obtained by dissolving a water-soluble polymer in water to form an aqueous solution of the polymer and then dispersing a water-dispersible polymer in the aqueous solution. 27. The method according to any one of concepts 10 to 26, wherein the binder is an aqueous composition prepared by dissolving at least one water-soluble polymer selected from the group consisting of polyvinyl alcohol and polyvinyl acetate and combinations thereof in water at a temperature of 10 to 100°C, in particular 15 to 100°C, at ambient pressure to form an aqueous solution of the polymer, and then dispersing at least one polymer selected from the group consisting of polyurethane dispersions, acrylic latexes, styrene-butadiene dispersions, binders in the solution at a temperature of 20 to 100°C, at ambient pressure. 28. The method of any one of concepts 14 to 27, comprising providing the binder as a stable dispersion. 29. A method according to any one of concepts 14 to 28, comprising mixing a sizing agent, in particular a reactive sizing agent such as alkyl ketene dimer or alkenyl succinic anhydride, with the binder. 30. A process according to any one of concepts 14 to 29, comprising foaming the aqueous composition, in particular in the absence of a surfactant. 31. Process according to any one of concepts 14 to 30, wherein 50 to 99 wt.%, in particular 60 to 90 wt.%, of the fibers of the fiber layer consist of cellulose or lignocellulose fibers or mixtures thereof and 1-50 wt.%, in particular 10-40 wt.%, of non-wood natural fibers or artificial fibers or combinations thereof. 32. The method according to any one of concepts 14 to 31, wherein the wood fibers are bleached or unbleached, refined or unrefined fibers selected from the group of pulp fibers, recycled fibers, mechanical pulp fibers and semi-mechanical pulp fibers and combinations thereof, in particular the wood fibers are selected from the group of substantially unrefined cellulose fibers, lignocellulose fibers and combinations thereof. 33. The method according to any one of concepts 14 to 32, wherein the artificial fibers are selected from the group of regenerated cellulose fibers, synthetic fibers, synthetic thermoplastic fibers and mixtures thereof. 34. The method of concept 33, wherein the regenerated cellulosic fibers are selected from the group consisting of viscose fibers, lyocell fibers, rayon fibers, and mixtures thereof. 35. The method according to any one of concepts 14 to 34, wherein the non-wood natural fibers are selected from the group of annual or perennial fibers, such as hemp, flax, kenaf, bagasse, cotton and straw and combinations thereof. 36. The method of concepts 14 to 35, wherein the thermoplastic fibers are selected from the group consisting of polyolefin fibers, polyester fibers, and biopolymer fibers, and mixtures thereof. 37. A method according to any one of concepts 14 to 36, comprising applying 0.1-20%, for example 0.5 to 15, such as 1 to 10 wt% of binder, calculated on the basis of the dry mass of the fiber layer. 38. A method according to any one of concepts 14 to 37, comprising producing a fiber web having a basis weight of 10-250 g / m 2 , especially about 20-200 g / m 2 . 39. The method of any one of concepts 14 to 38, wherein the fibers form a fiber network by hydrogen bonds or adhesive bonds. 40. A water-dispersible composite structure obtained by a process according to any one of concepts 14 to 39. 41. Use of a method according to any one of concepts 14 to 40 for producing nonwoven products selected from the group of nonwoven webs, nonwoven sheets or paper webs or paper sheets. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 5,346,541 [0003, 0090] US 3 563 241 [0005, 0090] US 5 629 081 [0006, 0090] EP 1 285 985 [0006, 0090] US 2014 / 0318726 [0007, 0090]

Claims

[1] Water-dispersible composite structure comprising a fiber layer, characterized by , that - at least part of the fibre layer consists of a fibre fabric or sheet containing 50-90% by weight of wood fibres, 10 to 50% by weight of non-wood fibres and 0.1-20% by weight of binder, calculated on the weight of the fibres, wherein at least part of the binder is a water-soluble polymer, and - wherein the fiber fabric or sheet is produced by wet forming technology, wherein a first part of the binder is formed by a water-soluble polymer or a polymer mixture and a second part of the binder is formed by a water-dispersible polymer or a polymer mixture, and wherein the binder contains at least one water-soluble polymer and at least one water-dispersible polymer in a weight ratio of 1:20-20:1, calculated on the basis of the dry mass of the polymers. [2] The water-dispersible composite structure of claim 1, wherein the wood fibers are bleached or unbleached, refined or unrefined fibers selected from the group consisting of chemical pulp fibers, recycled fibers, mechanical pulp fibers, and semi-mechanical pulp fibers, and combinations thereof. [3] Water-dispersible composite structure according to claim 1 or 2, wherein the non-wood fibers are selected from the group consisting of natural non-wood fibers and artificial fibers, in particular polymer fibers, which are selected, for example, from the groups - annual or perennial plant fibres such as hemp, flax, kenaf, bagasse, cotton and straw and combinations thereof; - thermoplastic fibers, e.g. polylactides (PLA), glycolic acid polymers (PGA), polyhydroxyalkanoates (PHA), polyolefins (PO), polyethylene terephthalates (PET), polyesters (PES), polyvinyl alcohols (PVA); - bicomponent fibres comprising thermoplastic polymers; - mineral fibers, glass fibers; - regenerated cellulose fibres, such as viscose fibres, lyocell fibres, rayon fibres; and - Combinations of fibers selected from two or more of the aforementioned groups. [4] Water-dispersible composite structure according to one of claims 1 to 3, wherein the non-wood fibers are short-cut fibers, in particular with a length of 5 to 25 mm, in particular 6 to 18 mm, and preferably a thickness of 0.5 dtex to 20 dtex, in particular 1 to 15 dtex, for example 1.5 to 10 dtex. [5] Water-dispersible composite structure according to any one of the preceding claims, wherein the binder is selected from the group consisting of polyvinyl alcohols, polyvinyl acetate dispersions, ethyl vinyl alcohol dispersions, polyurethane dispersions, acrylate latices, styrene-butadiene dispersions, binders based on finely divided cellulose, binders based on cellulose derivatives, biopolymers, such as biopolymers based on starch derivatives natural gum latexes, alginates, guar gum, hemicellulose derivatives, chitin, chitosan, pectin, agar, xanthan, amylose, amylopectin, alternan, gellan, mutan, dextran, Pullulan, fructan, locust bean gum, carrageenan, glycogen, glycosaminoglycans, murein, bacterial capsular polysaccharides and the like, and combinations thereof. [6] Water-dispersible composite structure according to one of the preceding claims, wherein the binder comprises a polymer selected from the group of polyvinyl alcohols, polyvinyl acetate dispersions, ethyl vinyl alcohol dispersions, polyurethane dispersions, acrylic latexes, styrene-butadiene dispersions, binders based on finely divided cellulose, binders based on cellulose derivatives, biopolymers and combinations. [7] A water-dispersible composite structure according to any one of the preceding claims, wherein the binder contains at least one water-soluble polymer and at least one water-dispersible polymer in a weight ratio of 1:10-10:10, calculated on the basis of the dry mass of the polymers. [8] A water-dispersible composite structure according to any one of the preceding claims, wherein the nonwoven fabric or fibrous web comprises a network of fibers held together primarily by hydrogen bonds or adhesive bonds. [9] A water-dispersible composite structure according to any one of the preceding claims, wherein the nonwoven fabric or sheet further contains a sizing agent, in particular a reactive sizing agent such as alkyl ketene dimer or alkenyl succinic anhydride. [10] A water-dispersible composite structure according to any one of the preceding claims, wherein the sizing agent is alkyl ketene dimer or alkenyl succinic anhydride. [11] A water-dispersible composite structure according to claim 8, wherein the sizing agent is mixed with the binder(s). [12] A water-dispersible composite structure according to any one of the preceding claims, wherein the fiber web or sheet is dispersible in an aqueous medium at a temperature of 10 to 75°C and a pH of 6 to 8. [13] A water-dispersible composite structure according to any one of the preceding claims, comprising a fiber fabric or sheet having a basis weight of 10-250 g / m2 , especially about 20-200 g / m 2 . [14] A water-dispersible composite structure according to any one of the preceding claims, comprising a fibrous web or sheet selected from the group of nonwoven webs and sheets. [15] A water-dispersible composite structure obtained by a process for producing a water-dispersible composite structure containing a layer of wood fibers, non-wood fibers and a binder, the process comprising the steps of: - conveying an aqueous fiber pulp to a perforated support, wherein the fiber pulp conveyed to the perforated support comprises chemical fibers or natural non-wood fibers or combinations thereof together with cellulose fibers, lignocellulose fibers or a mixture thereof; - draining liquid through the perforated support to form a fiber layer; and - applying a binder to the fiber layer to at least partially bind the fibers, wherein the binder comprises an aqueous solution of a water-soluble polymer further containing a water-dispersible polymer, wherein the binder contains at least one water-soluble polymer and at least one water-dispersible polymer in a weight ratio of 1:20-20:1, calculated on the basis of the dry mass of the polymers.

Images